Safes and other secure containers have traditionally used combination locks for controlling and authorizing entry. Early locks were entirely mechanical and relied on a person dialing a correct combination on a rotating dial. Rotation of the dial positioned mechanical elements within the lock such that dialing the correct combination allowed a locking bolt to release the container door. Proper dial rotation aligned gates in tumblers. Once the gates were aligned, a fence on a fence lever entered the aligned gates. Continued rotation of the dial and tumblers pulled the fence lever and withdrew the bolt.
However, over the years electromechanical locks have gradually replaced the mechanical locks described above. Indeed, electromechanical locks themselves have seen many improvements over the years. The use of sophisticated electronic logic circuitry has enabled the implementation of a series of complex and unique electronic combinations which has made improper entry into secured areas more difficult. When the lock is used to secure entry to a container, the electronic components are typically mounted within a housing inside the container door. The housing contains an actuating device and a circuit board. The electronic key pad transmits a signal to the circuit board, which contains the electronic circuitry that allows the lock to open and close. The keypad is located on the outside of the housing so as to be accessible to the user. A cable typically extends between the keypad and the circuit board for transmitting signals between the two components.
In addition to the electronic circuitry, electromechanical locks include a bolt. The bolt is movably constructed and is coupled to a bolt-displacing device enabling a user to selectively move the bolt into one of at least two end positions by means of the actuating device. The lock is blocked and therefore “locked” in a first end position of the bolt and unblocked or “open” and “unlocked” in a second end position of the bolt. When the user enters the correct combination into an electronic keypad, a signal is transmitted to the circuit board. The circuit board in turn actuates the actuating device, which allows the locking bolt to move to the unlocked position within the housing, thus allowing the user to open the safe door.
Although known electronic locks have proven effective in everyday practical use, there is a need for improvement, particularly with regard to design. For example, electrical surges in the power line supplying power to the electronic lock can damage the circuitry making impossible the opening of the lock by the authorized user. The resultant cost to have the safe or secured area opened could be significant in light of the materials used for the enclosure and the difficulty in gaining entry by cutting through those materials. In addition, malfunction could also result from tampering, or loss of power making opening of the lock impossible.
Accordingly, there is a need for a combination mechanical and electronic lock that is simple to assemble, cost efficient, and that can reliably block access to a container by unauthorized users.